DESCRIPTION: (Applicant's abstract) This application is focussed on the signal transduction of dopamine. Recently, the applicant and several other investigators have demonstrated that some actions of dopamine in the brain may be mediated through the phosphoinositide signaling cascade rather than the classic adenylyl cyclase system. The goal of the proposed project will be to elucidate the mode and mechanisms of functional regulation in the phospholipase C coupled dopamine system. There are three primary questions to be addressed by the experiments: (1) Where in the brain does dopamine signal through the phospholipase C pathway?; (2) Which G-proteins mediate dopamine receptor coupling to phospholipase C?, and (3) How is the efficacy of dopamine receptor coupling to phospholipase C regulated?